Goldox. At many major airfields, vehicles operating on the manouevring area, e.g. aircraft tugs, safety service vehicles, lawn mowers, etc., use UHF. The UHF frequency is linked to the appropriate VHF frequency such that whenever anyone transmits on either frequency they will be heard on the other. The reason for this is lost (to me) in the mists of time but it maybe because the drivers of those vehicles are not licenced to operate in the airband. The man sitting on GMC hears all the stations, apparently on one frequency, but in the case of severe interference he can deselect the cross-coupling system so he does not hear on the UHF channel.
ukdean... Just make sure you get an aerial to cover the frequencies you are interested in. VHF and UHF are far more "aerial critical" than HF. For HF you can throw up any fairly long wire and get results but if you have a wrongly matched aerial on VHF it can seriously degrade signal reception.
Lastly, we are currently just into this year's Sporadic E season. During the next couple of months some VHF transmissions maybe heard over very considerable distances instead of just line of sight.